<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        html{
            font-size: 10px;
        }
        .outer{
            font-size: 32px;
            width:50vmax;
            height: 20vh;
            background-color: green;
        }
    </style>
</head>
<body>
    <div class="outer">
        文字
    </div>
</body>
</html>